Apparatus or the fluid current type for desiccating foodstuffs



proved apparatus for.

Patented Aug. 16, 1949 ,APPARATUS oF THE .Foa DEsIcoArrl NGFOODSTU-FFS Arthur -W. rKo'on; Luling, 12a, Application October Y15, 1945,y SerialNoi- 622,3[6

(Crees- 19t 4 Claims; 1

The present invention-,relates to the art ofdesiccating moisture-containing solids andA semisolids which are-of such a particle size as to be susceptible'of being carried. ina gas streannand is particularly concerned with improvements in a process of, and more especially with an iintreati'ng, i. e., curingf freshly-cut limmature forage crops' and fodder, dehydrating -freshly `gathered leafy vegetable matter, drying matured seedandroot crops, and

desiccating other moisture-containing foodstuis and the like; which-.process and, apparatus were May 20, 1930, to :Arthur W..Koon. Y

Generically considered,` the lprocess.comprises `introducing astream of lparticles of theA moisture-containingmaterial-to beV desiccated into a high-velocity currentot gaseous kdry-ing vmedium comprising or consisting essentially of 'a Yproperly ,proportioned mixturefof steam andinert gaseous combustion -products 'which' medium is maintained at an elevated temperature materially above the dew fpoint ,thereonmaintainingv free suspension of the-material inthe gaseouslmixture during the travel ofthe. latter for arelatively brief period ottime, andfseparating the material -from the Agaseousn'lixture*out-ot contact with atmospheric air and while. the-gaseous mixture is vat av temperaturefmaterially -above -its dew point.

For-effecting thisggeneral process with bestresults, I have-found--it-advisableto supplement rthe same by the followinggprocedural features (i) Before 'the particles of moisture-containing material are suspended. in theghig-h-tempera- Y ture Ygaseous mixturerthe stream ofsparticlesf is substantially purgedof associatedA atmospheric `air by scrubbingthe same withy a` current of the -aoresaidgaseous mixture 'at anintermediate elevated temperatura-totheend that` oxidation,

scorching -or burningv ofY thematerial while undergoing the Aensuing, high-temperature drying treatment, involving Athe applicationof. heat at or above the lrindlingv temperaturel or the. material, islminimized or avoided.-

(2)Y After the-aforesaid removal of atmospheric air, and before` the material issuspended inthe high-velocity current of` high-temperature gaseous -miXtureVi-,he material to be f desiccated preferably yis pre-heated by intimate. contact with a current of the same gaseousfmixture at a Ytem.-

Vperature materiallyabove itsdew `point but preferably lower than thatfatfwhich the -current of gaseous mixtureis .maintained during at least a part of the period in which the :particles of material are suspended' therein.A lB'yrecou'rse to this 'fied'l air. p y x Y n i 'may be and preferably is furthercooled before 'being 'stored' or distributed.

Ypre-heating step-dehydration of the material is initiated and c arrie'd'to such 'a degree that the particles off-material. lare rendered readily 'sus'- pendable in-'the gaseous current, 'and that "the satisfactorily completeldesiccation o 'the ma-V terial canbe eii'e'cted'in a single cycle or passof high-temperature idesiccation treatment. 1

(3')y During thetra'vel f the high-temperature gaseous current carrying particles of thel` material freely suspended'therein the 'desired' high velocity is wrnaiiitaed'by lthe' use'of 'a plurality f`.centrifu'ga1blcwers operating; in series.

f4) Also,v during said 'travel hgh-'temperature heat is impartedtothegaseousi current in a 'plurality of stages, whereby'to maintain the current Y at the desired hightemperature ortemperatures `ISuch stage-wiseHeatingpreferably although not necessarily, is effected byintroducing 'high-tem'- perature inert; igaseous'combustion products di*- rectly into said current `Aat spacedV intervals along vits course.

(5) After Vthe, dehydrated `material has'been separated, y at a high temperature, from the current"dfgaseous'drying medium it still'v is associated" with 'some 'oifthe'steam-containing mixture,

'were it 't'o .becocled 'to below Ithe dew point 'in ycontact therewith; To ayoidfthis, and simultaneously to reduce thetemperature of thefdeli'ydrated material; Ifsubstantiallyreplace the moisture-laden 'gas' with` a VgasQof' a desirably low `nulmidit'y by re-susp'ending theseparat'ed material inA a'current `of such low-humidity gas, at an'eleivated temperature materially lower than that of the 'aforesaid mixturefand then separating the sc-treatedjmaterial Vfrom the current of suspending gas. This su'spending gas maybe 'a current ofJhot lor warm partially'orcompletely dehumidi- The 'dehydrated material kthereafter The apparatus'"fr use' in eilecting the improvedY process "o"f"the "present invention essentially consists in an assemblage of members cooperating "to constitute'an essentiallyy closedcircuit for circulating a -currentl of high-temperature inertV gaseous drying, mediumv comprising .steam and gaseous combustion products, together iwith 'other associated devices.r This closed circuit a's'seniblage`includes: means kfor advancing a stream 'of' 'the material to be. 'desiccated means for purging air from tle advancing. material, va

material-suspending means, a separator for removing solid"partlcles 'suspended' in a carrying gas, a 'circuitbu's'i conduit connecting the/material-suspending means with the separator, one or more blowers interposed in the circuitous conduit, a return conduit for leading gas (freed from suspended particles) from the separator to the material-advancing means, a fluid fuel burner associated with the material-suspending means and adapted to discharge thereinto high-ter.- perature inert gaseous combustion products, and a plurality of high-temperature heating means associated with the circuitous conduit which latter heating means may be and preferably are fluid fuel burners discharging their high-temperature inert gaseous combustion products directly into the gas current being maintained in said circuitous conduit. For maintaining a desirable balance in this system, there is provided a venting means for exhausting excess gaseous drying medium. Such venting means may be and preferably is a part of the aforesaid air-purging means. In association with the closed system assemblage above described there are the following pieces of equipment: a second separator, a source of hot or warm relatively dry gas (e. g., dry air), a third conduit communicating between the dry gas source and the second separator, a blower for maintaining a current in said third conduit, and means for feeding into this latter current a stream of solid particles from the rst named separator; also, there preferably is provided a feeding means for feeding a stream of material to .be desiccatedV into functional proximity to the material-advancing means. Lastly, there may be and preferably are provided a third separator, a fourth conduit, a source of relatively cool and dry gas (e. g., of dehumidied ambient air), a blower for maintaining a current Vschematic view of Va system of apparatus adapted for use in carrying out the process of the invention. According thereto, a vented hopper A is mounted above and adjacent one end of, and communicating with, an elongated rectilinear enclosure B housing an endless conveyor actuated by conventional means (not shown). The opposite end of enclosure B communicates with the inlet end of a rotary drum C having generally closed ends. Conventional means (not shown) are provided for suspending and rotating drum C. Between the inlet from A and drum C there is provided in enclosure B an opening for the introduction into B of a current of gas as from conduit L. N is an exhaust conduit for discharging gas to atmosphere from that end of enclosure B which is remote from drum C.

D is a circuitous conduit communicating -between drum C and a cyclone separator F. E-I and E-Z diagrammatically represent two motor- Vdriven centrifugal blowers which are interposed combustion products into the gaseous drying medium adjacent the inlet end of drum C, whereby to raise the temperature of the medium to the desired level, e. g., to say 1000 F. or above. Km2, K-S, K-4 and K-S similarly represent a plurality of uid fuel burners or ring tunnels discharging high-temperature, inert, gaseous com- .bustion products into the current of gaseous drying medium circulated through conduit D. Branch -conduits M from conduit L serve to divert gas from the latter through K-l and into the inlet end of drum C.

It should be observed that so much of the apparatus as has now been described provides what is in eiect a closed system in that a gaseous drying medium can be circulated from E through L to B to C and through D to F again. In operation: the material to be dried, in appropriate cases after having been reduced or cut into small pieces by means of an ensilage cutter or equivalent chopping device (not shown), is introduced into hopper A, and by the latter is fed to the conveyor in enclosure B. As the subdivided material is advanced towards drum C it is swept by a current of a hot (e. g., say 300 F.) mixture of steam and inert gaseous combustion products from conduit L: during the initial stage of the movement of the material through B, i. e., between the inlet from A and the inlet from L, its direction of travel is counter to that of excess gas mixture exhausting to Vatmosphere through conduit N, whereby atmospheric air is purged from the material; during the subsequent stage, the air-free material moves co-currently with the gas mixture passing from L into drum C. An excess of gas mixture, over andl above the demands of the .blower units used to move the material through the system, is created by (a) expansion of the water (in the product) into steam and by f (b) the continuous introduction of the high-temperature, inert, gaseous combustion products into the system.

As drum C revolves, the lighter and drier particles of material fed thereinto from B are suspended in the gas current passing therethrough. The heavier (e. g., wetter) particles, being exposed to the heated gas current, lose water to the latter by evaporation and likewise become suspended in said current and are carried into the flow line (in conduit D) which passes, and receives high-temperature inert gaseous combustion gases from, combustion chambers or firing tunnels K2, K3, K4 and K5. Sufficient heat, at a sufliciently elevated temperature level, is supplied directly tothe current by these latter to drive off the moisture from within the particles during their relatively very brief course of travel in said flow line. By proper adjustment of the feed of uid fuel and combustion air to the ring tunnels or combustion chambers (K-I-KE) substantially perfect combustion is realized, thereby obviating the introduction of vunburnt fuel of free air into the ow line. The necessary highV velocity is imparted to the current by the tandem blowers El, E2. In separator F the dehydrated particles are separated from the current of gas mixture which had carried them through conduit D. The gas mixture eilluent from separator F passes through conduit L and largely to the inlet end of drum C by way either (a) of enclosure B or (b) of branch conduits M and burner KI. A controlled amount of the gas mixture delivered by conduit L to enclosure B is exhausted through the latter to atmosphere by way of exhaust conduit N. Any further excess of gas mixture may be vented directly to the atmosphere through suitable damperedpipes (not shown), whereby to maintain a self-balancingsystem.

The aforesaid separation (as'between dehydrated particles and drying mediuml current) does not serve to free the particles from entrained gas mixture. Moreover, the entrained gas mixture is laden nwith moisture which latter would condense on the particles were the latter to be cooled toA below the dewl point in contact with the gases. Accordingly, Iprovide means for separating'the moisture-laden gases from the dehydratedmaterial at elevated temperature, which means now will be described.

At the bottom of separator F there is provided adumping gate G located above and discharging into a conduit H. This latter, in which a centrifugal blower E34is interposed, communicates between a source of hot air and a higheciency collector I provided with a dumping gate Q. J diagrammatically represents a thermally insulated but not air-tight enclosure with, in which drum C is housed. The open end and end portion of circuit H on the suction sideof blower E3 are llocated within enclosure J above drum C, and blower E3 draws hot air from within said enclosure by way of conduit H andcreates a current of said hot air passing through conduit I-I and to collector I. I l

O represents a Vsource of relatively cool air of controlled low humidity, E4 a blower, P a conduit communicating between VO andthe suction side of the blower, S a cyclone" separator provided with a bagger for jseparated'solids, and R a conduit communicating between E4 and S.` y

Particles discharged by dumpingl gate G from separator F into conduit H are suspended in the current of hot air from enclosure J and by the current are transported into collector I. In the course of the travel of the particles through conduit H, moisture laden gas Avery largely is scrubbed from the particles by the suspending air, to the end that the particles separated out of the current discharged into collector'I are associated with a gas (air) of relatively low moisture content only, in which association the particles can, under suitable conditions of atmospheric humidity, be cooled to below the dew point Without danger of condensing moisture thereon. Dehydrated particles are discharged from'collector I through-dumping gate Q into conduit P, are suspended in a current of cool, low-humidity air from source O, or directly from the atmosphere, and are carried in said current to separator S wherein they are collected for immediate use or for packaging (e. g., bagging)` for shipment or storage.

Source O may be any suitable air dehumidifying device of known type. Its use may be and generally is restricted to those occasions when the ambient air is unduly humid: when the ambient air is desirably dry this latter may, without dehumidication, provide the gas current in conduits P and R.

It is to be appreciated that in the carrying out of the above described process the material to be desiccated is subjected to the highest temperature condition only after having been purged of initially associated atmospheric air and only at a time when said material is freely suspended in a relatively high-velocity current of the inert (i. e., non-oxidizing) gaseous drying medium, consisting essentially of steam and inert gaseous combustion products, in a substantially closed system. It is to be appreciated, also, that after the so- Y ing means, a material-suspending desiccated material has been'separated from the bulk of the moisture-laden drying medium itis substantially freed from entrained moistureladen gas while maintained at an :elevated temperature at which moistureY does not'condense and thereafter is associated with a gas of relatively lowhumidity during at least the initial part of its cooling. These procedural features make possible a substantial simplication of the apparatus and process.

I claim: Y y

l. A system of apparatus foruse indesiccating moisture-containing foodstuffs, fodder, forage and like material, comprising, in combination, an essentially closed circuit for circulatingpa current of high-temperature vinert gaseous drying me-A dium, said circuit including: a material-advancmeans cooperating therewith, a separator, a circuitous conduit connecting the material-suspending' means 'with the separator, a current-inducing means interposed in said circuitous conduit, a plurality of fluid fuel burners arranged to introduce hightemperature inert gaseous combustion products inte said circuitous conduit at spaced intervals therealong, a return conduit connecting the separator with the material-advancing means,a fluid fuel burner arranged to discharge hightemperature gaseous combustionl products into said material-suspending means, and a branch conduit communicatingbetween the return conduit and the last-mentioned burner, the'several members above recited cooperating to constitute Athe aforesaid essentially closed circuit; means associated with the material-advancing AYmeans for venting excess gaseous drying medium from the circuit into they atmosphere in counter-current contact with material being advanced into the'circuit, a second separator, a source of warm relatively dry gas, a third conduit communicating between said source and'said second separator and provided with a blower for maintaining a current of warm relatively dry gas from said source to said second separator, and means for feeding material from the separator of the closed circuit into said third conduit.

2'. YA system of apparatus for use in desiccating moisture-containing foodstuffs,v fodder, forage Yand likeV material, comprising, in combination,

an essentially closed circuit for circulating a current of high-temperature inert gaseous drying medium, said circuit including: a material-advancingineans, a rotary'drum member cooperating therewith, a separator, 'a'lcircuitous conduit connecting the rotary drum member with the separator, at least one blower interposed in said circuitous conduit and arranged to maintain a high-velocity current of gas from said rotary drum member through said circuitous conduit to said separator, a plurality of fluid fuel burners arranged to introduce high-temperature inert gaseous combustion products into said circuitous conduitat spaced intervals therealong, a return Vconduit connecting the separator with the material-advancing means, a fluid fuel burner arranged to discharge high-temperature gaseous combustion products into said rotary drum member, and a branch conduit communicating between the return conduit and the last mentioned burner, the several members above recited cooperating to constitute the aforesaid essentially closed circuit; means associated with the material-advancing means for venting excess gaseous drying medium from the circuit into the atmosphere in counter-current contact with material being; ,advanced-iintoftheV circuit, a second-separai913;` aasource of warm'relatively dry gas, a third conduitrcommunicating betweensaid source and saidsecondrseparator and-provided with a-blower Vfor-Inaintaining a current of warm relatively dry gas-,from said source tosaid secondseparator, and; means for feeding material from the sepn araitor of theclosecl circuit into-said third conduit'. q

3. A system of apparatus for use in-desiccating moisture-containing foodstus, fodder, forage and likefmaterial, comprising., in combination, an essentially closed circuit for circulating a current of, high-temperature inert gaseous dryinginedium, saidcircuit including: a materialadvancingimeans, amateralsuspending means cooperatingtherewith, a separator, a circuitous conduit connecting the. material-,suspending means with theA separator, a current-inducing meansA inter- .posedinV said circuitous conduit, a plurality of iiuidvfuell burners arranged to introduce nightemperature inert gaseous combustion products into-said circuitous conduit at spaced intervals therealong, a return-conduity connecting the sep arator` with the material-advancing means, a fluid fuel burner arranged to discharge high-tempern atui'e'gaseous combustion products into said material-suspending means, and a branch conduit 4communicating between the return conduit and thelastmentioned burner, the several members above recited cooperatingto constitute the aforesaidrssentially closed circuit; means associated wlhtne material-advancing means for venting excess gaseous drying medium from the circuit intothe` atmosphere in counter-current contact y with material being advanced into the circuit, a-sBCOIld Separator, a source of warm relatively gas, athird conduit communicating between said sourceV and, said second separator and provided with a blower for Vmaintaining a current of-r warm relatively dry gas from said source to said secondseparator, means for feeding material fromthe separator` of the closed circuit into .said third conduit, a third separator, a source of; relatively cool and dry gas, a fourth conduit communicating between said source and said separator and provided with a blower for maintainingftherein a current of relatively cool and dry gasl from saidsource to said third separator, and means for feeding material from said second separator into said fourth conduit.

4. A systemof apparatus for use in desiccating moisture-containing foodstuffs, fodder, forage and like material, comprising, in combination, aron ytary drum having generally closed inlet and outlet ends, anfinsulating-housing about the rotary dr-um, an endless conveyor housed within an elongated rectilinear enclosure and adapted to forward a. stream of thematerialto be desiccated to the inlet end of theV rotary drum, gas-venting means in association with that end of the conveyorv enclosure which is remote from the rotary drum, means. for deliveringv avstream of the material, to said conveyor at av point remote from thel rotary drum, a` cyclone rseparator provided with an inlet port, ,an outlet port for separated gasV and a discharge port for separated solids, a circuitous conduit communicating between the outletlend of the rotary drum and the inlet port of: the separator, atleast one blower interposed inthe circuitous conduit for maintaining a current` of gas fromthe rotary drum to the inlet port of theseparator, a plurality of high-tem, perature heating means atspaced intervals along the circuitous conduit, a. second conduit com,- municating4 between the gas outlet portv of the separator4 andthe conveyor enclosure at a locus onthe latter intermediate the-material delivering means andthe rotary drum, a uid fuel burnerin communication with the inlet end of the rotary drum, at least one. branch conduit communicating between saidsecond conduit and said uid fuely burner, a second. separator provided with an inlet port, a vent for separated gas and, a4 discharge port for separated. solids, a third conduit communicating between the housing of the rotary drum and the inlet portv of the, second separator, a blower interposed. in sadthird conduit for maintaining a current of gas from said drumhousingto said secondseparator-,and means for deliveringlastream' of solids from the solids discharge port of said iirst separatorl into said. third conduit at a locus intermediate saiddrum housing and said blower.

ARTHUR. W. KOON.

Y REFERENCES CITED Theviollowing referencesare of; record'inthe iile ofthis patent:

Arnold Nov. 2l, 1944 

